Multinuclear {90 -complexes having at least two metal-cobalt bonds

ABSTRACT

Multinuclear cobalt carbonyl pi -Complexes having metal-cobalt bonds and which are useful as catalysts for the dimerization of norbornadiene are represented by the general formula: Z4 mMCom(CO)4m 2nYn WHEREIN M is a Group 4a metal, Z is a halo, nitrato, alkyl, aryl or similar ligand, Y is a pi -bonded diolefin ligand, m is 2, 3, or 4, and n is 1, 2, 3, or 4, but not greater than m.

United States Patent Tsai et al. 45 July 11, 1972 [54] MULTINUCLEAR w-COMPLEXES 3,141,031 7/1964 Wilkinson ..260/439 HAVING AT LEAST TWO METAL- 3,345,390 10/1967 Wilkinson.... ..260/429 COBALT BONDS OTHER PUBLICATIONS [72] i 8" g fi Schrauzeretal. J. Am. Chem. Soc. 88 (1967) p. 4890-4 g omnna mane 0t 0 Patmore et al. (I) Inorg. Chem. 5 (1966) p. 2222- 6 am a Patmore et a]. (ll) Inorg. Chem. 5 (1966) p. 1405-- 7 [73] Assignee: The Dow Chemical Company, Midland, Bonati at 1 Chem- 1966 P- 1052 5 Mich.

Primary Examiner-James E. Poer [22] Flled 1969 Assistant ExaminerA. P. Demers [21] Appl, No; 879,608 Attorney-Griswold and Burdick, R. G. Waterman, L. J. Dankert and M. S. Jenkins [52] US. Cl. ..260/429 R, 252/431 R, 252/431 N, 7 ABSTRACT 260/429.7, 260/435 R, 260/439 R, 260/439 CY, [5 1 260/666 R Multinuclear cobalt carbonyl 1r-Complexes having metal- [51] Int. Cl ..C07f 7/00, C07f 7/24, C07f 15/06 cobalt bonds and which are useful as catalysts for the [58] Field of Search .260/429, 429.7, 439, 435 dimerization of norbornadiene are represented by the general formula: Z ,,,MCo,,.(CO)4m -M ,1 [56] References Cited wherein M is a Group 4a metal, Z is a halo, nitrato, alkyl, aryl UNITED STATES PATENTS or similar ligand, Y is a rr-bonded diolefin ligand, m is 2, 3, or

4, and n is l, 2, 3, or 4, but not greater than m. 3,030,396 4/1962 Gorsich ..260/429.7 3,099,667 7/1963 Gorsich ..260/429 22 Claims, No Drawings MULTINUCLEAR ar-COMPLEXES HAVING AT LEAST TWO METAL-COBALT BONDS BACKGROUND OF THE INVENTION This invention relates to a new class of organo-cobalt compounds, and more particularly, to multinuclear, cobalt carbonyl qr-compleXCS having metal-cobalt bonds.

Binuclear, diolefin cobalt carbonyl complexes of the types, Co (CO) (diolefin) and Co (CO) (diolefin), in which the carbonyl groups bridge the Co-Co bond have been prepared by the direct interaction of dicobalt octacarbonyl with various diolefins such as 1,3-butadiene and isoprene.

Multinuclear, cobalt carbonyl, Ir-complexes having at least two metal-cobalt bonds have not been previously known.

SUMMARY OF THE INVENTION In accordance with the present invention, multi-nuclear, cobalt carbonyl Ir-complexes having at least two metal-cobalt bonds are provided. Such qr-complexes are represented by the general formula:

wherein M is a metal of Group 4a of the Periodic Table of Elements, Z is a ligand selected from the group consisting of halo, nitrato, alkyl and aryl, Y is a 'rr-bonded diolefin ligand, m is 2, 3, or 4 and n is l, 2, 3, or 4, but not greater than m. For the purposes of this invention alkyl includes alkyl, cycloalkyl and substituted alkyl such as haloalkyl and aryl includes aryl and substituted aryl such as haloaryl.

These multinuclear rr-complexes are useful as catalysts for the dimerization of norbornadiene and substituted norbornadienes. Said complexes are also suitably employed in the polymerization of other olefins such as allene. The multinuclear vr-complexes wherein Z is halo are particularly effec tive in the stereospecific dimerization of norbornadiene. The rr-complexes may also be employed as chemical intermediates in the preparation of other complexes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The novel compounds of the present invention are characterized as multinuclear, cobalt carbonyl rr-complexes having at least two metal-cobalt bonds. By a multinuclear complex is meant a compound having at least 3 metal atoms including the cobalt atoms per molecule. The carbonyl ligands of the novel rr-complexes of this invention are bonded to the cobalt atoms and do not bridge the cobalt atoms. These complexes are classed as tr-complexes since they contain diolefin ligands which are ar-bonded to the cobalt atoms. These novel multinuclear, rr-complexes are generally represented by the formula: Z., ,,MCo,,,(CO),,,, ,,Y, wherein Z, M and Y are described hereinafter in more detail and m is 2, 3, or 4 and n is 1,2, 3, or 4 but not greater than m.

More specifically M is a metal of Group 4a of the Periodic Table of Elements, Handbook of Chemistry and Physics, 48th ed., The Chemical Rubber Company. Illustratively, M includes tin, germanium, silicon, and lead, preferably tin and germanium.

Specifically Z is an inorganic or organic ligand. Suitable inorganic ligands are selected from the groups consisting of halo, such as fluoro, chloro, bromo and iodo; and nitrato. Preferred inorganic ligands are bromo and chloro. Suitable organic ligands include alkyl and substituted alkyl wherein the substituent is aryl, halo, alkoxy, amino and the like; cycloalkyl and substituted cycloalkyl; aryl and substituted aryl wherein the substituent is alkyl, halo, alkyoxy, amino and the like; and related organic groups. Preferred organic ligands include phenyl and alkyl wherein alkyl has one to four carbon atoms.

In defining Z, it is to be understood that Z can be more than one of the above described ligands in a single molecule of the multinuclear 1'r-complex. For example, a complex represented by the structure:

is contemplated. Also contemplated arc complexes represented by the general structure:

and

where Y and Y may be, e.g. norbornadiene and butadlene, respectively.

Specifically Y is a 1r-bonded diolefin ligand having from three to 10 carbon atoms, preferably from four to eight carbon atoms. In the complex, Y is rr-bonded to a cobalt atom. Illustratively, Y includes acyclic conjugated alkadienes having from four to eight carbon atoms, e.g., buta-l,3-diene, isoprene, panta-l,3-diene, 2,3-dimethylbuta-1,3-diene, hexa- 1,3- and hexa-l,4-diene, octa-2,4-diene, 2-methylpenta-l,3- diene, and the like; alkoxy substituted acyclic conjugated alkadienes, e.g., 2-methoxybuta-l,3-diene, 2,3-dimethoxybuta- 1,3-diene, 2-methoxy-3-ethoxypenta-l,3-diene, and the like; cyclic alkadienes, e.g., cyclopentadiene, cyclohexa-l ,3-diene, cycloocta-l ,3-diene, cyclohexa-l,4-diene, cyclohepta-l ,3- diene, cyclohepta-l,4-diene, cycloocta-l,5-diene, and the like; aryl substituted acyclic conjugated alkadienes, e.g., 1,4- diphenylbuta-l,3-diene and the like; polycyclic alkadienes, e.g., norbornadiene and substituted norbornadienes, bicyclo- [2.2,0]hexa-2,5'diene, spir0[4.4]nona-l,3-diene, Spiro-[4.2] hepta-l,3-diene, bicyclo[4.2.0]octa-2,4diene, bicyclo[3.3.0] octa-l,3-diene,bicyclo[3.2.l.,]octa-2,6-diene and the like.

Preferably the diolefin ligand is norbornadiene, substituted norbornadienes, conjugated alkadienes and substituted alkadienes having from four to eight carbon atoms and the like.

Representative multinuclear vr-complexes include, for example, dichlorobis(norbornadienedicarbonylcobalt)tin-(IV), dibromobis( norbomadienedicarbonylcobalt)tin( IV dimethyland diphenylbis(norbornadienedicarbonylcobalt)- tin(lV), dichloro(norbornadienedicarbonylcobalt)(tetracarbonylcob'alt)tin(lV), dibromo(norbornadienedicarbonylcoba lt)(tetracarbonylcobalt)tin(IV), dimethyland diphenyl-(norbornadienedicarbonylcobalt)(tetracarbonylcobalt)tin-(IV), dichloroand dibromobis( l ,3-butadienedicarbonylcobalt)tin(IV), dichloroand dibromo(1,3-butadienedicarbonylcobalt)(tetracarbonylcobalt)tin(IV), chloroand bromo(norbornadienedicarbonylcobalt)bis(tetracarbonylcobalt)tin(IV), chloroand bromobis(norbornadienecarbonylcobalt)(tetracarbonylcobalt)tin-(IV), chloroand bromotris(norbornadienedicarbonylcobalt)tin(lV), phenylethylbis-(buta-l ,3-dienedicarbonylcobalt)germanium(IV), diphenylbis(norbornadienedicarbonylcobalt)germanium(IV), chlorophenylbis(isoprenedicarbonylcobalt)lead(IV), methyltris-(cyclopentadienedicarbonylcobalt)silicon(IV dinitrobis- (cyclohexa-l ,3-dienedicarbonylcobalt)tin(IV), dibromocyclohexal ,3-dienedicarbonylcobalt)( tetracarbonylcobalt)- tin( IV di-iodo(cycloheptal ,4-dienedicarbonylcobalt (cyclooctal ,5-dienedicarbonylcobalt)silicon(lV dibromobis(cyclohexa-l ,3-dienedicarbonylcobalt)tin(IV dichloro-( 1,3-butadienedicarbonylcobalt)(norborna dienedicarbonylcobalt)germanium(IV), chloroand bromo(norbornadienedicarbonylcobalt) (butal ,3-dienedicarbonylcobalt)(tetracarbonylcobalt)tin(IV), ethylbromobis(cyclopentadienedicarbonylcobalt)lead(lV) and various homologues of these complexes.

The novel multinuclear 1rcomplexes of the present invention are advantageously prepared by a two step procedure. In the first step a complex having the general structure Z,, ,,,MCo (CO) is made and in the second step the product of the first step is contacted with the desired diolefin to yield the multinuclear Ir-complex.

In the instance wherein Z is halogen and m is 2, the first step involves reacting a metal compound, MX with X representing halogen greater than fluorine with an equimolar amount of dicobalt octacarbonyl in an ether or alcohol diluent to form an insertion product having the structure For the compound in which Z is a halogen and m is 3, the reaction involves contacting 1 mole of MX with 2 moles of dicobalt octacarbonyl in the same type of organic solvent to form the product having the structure In the instance wherein m is 4, the reaction involves contacting 1 to 2 moles of MP with a mole of dicobalt octacarbonyl in the same type of organic solvent to form the product having the formula M[Co(CO),,] The compounds wherein m is 2 or 3 can also be prepared by reacting a mole of anhydrous metal compound, MX with 2 moles or 3 moles, respectively, of sodium tetracarbonylcobaltate-( l-).

In the instance wherein Z is an organic ligand such as alkyl, aryl, etc., the first step involves reacting an organo metallic compound, R MX or RMX with X representing halogen and R representing the organic ligand, with a slightly excess amount, say about 20 percent, of sodium tetracarbonylcobaltate( l-).

in the instance wherein Z is nitrato, the first step involves preparing the compound by one of the aforementioned methods and subsequently reacting the compound with a methanol solution of silver nitrate.

Among the metal compounds, MX which are suitable for the preparation of the insertion product wherein Z is halogen are the Group 4a metal dihalides such as tin(ll) chloride, tin(ll) bromide, tin(ll) iodide, tin(ll) fluoride chloride, tin(ll) bromide chloride, germanium(ll) chloride, germanium(ll) bromide, germanium(ll) iodide, lead(ll) bromide, lead(ll) iodide, lead(ll) bromide chloride, silicon(ll) chloride, silicon- (ll)bromide, and silicon(ll)iodide, with the dihalides of tin and germanium being preferred.

Metal compounds, MX,,, which are suitable for reaction with sodium tetracarbonylcobaltate(l-) or the like are the Group 4a metal tetrahalides such as tin(lV) chloride, tin(lV) bromide, tin(lV) fluoride, tin(lV) iodide, tin(lV) bromide trichloride, tin(lV) dibromide dichloride, tin(lV) tribromide chloride, tin(lV) dibromide diiodide, tin(lV) dichloride diiodide, germanium(lV) fluoride, germanium(lV) bromide, germanium(lV) chloride, germanium(lV) iodide, germanium(lV) dichloride difluoride, germanium(lV) trichloride fluoride, silicon(lV) chloride, silicon(lV) bromide, silicon(lV) fluoride, silicon(lV) tetraiodide, silicon(lV) dibromide dichloride, silicon(lV) chloride trifluoride, silicon(lV) tribromide chloride, lead(lV) chloride, and the like.

Among the organometallic compounds, R MX or RMX which are suitable for preparing multinuclear rr-complexes wherein at least one of Z is an organic radical are the Group 4a organometallic dihalides and organometallic trihalides. Examples include dimethyldichlorosilane, diphenyldichlorosilane, dibromodiethylsilane, diethyldichlorosilane, dipropylfluorochlorosilane, dibenzyldichlorosilane, phenylethyldichlorosilane, diethyltin dibromide, diethyltin dichloride, dipropyltin difluoride, di-n-butyltin diodide, diisopropyltin dibromide, diphenyltin dichloride, di-o-tolytin dichloride, methyltin trichloride, divinyltin dichloride, phenyltin tribromide, ethylpropyltin dichloride, diethylgermanium dibromide, dimethylgermanium dichloride, diphenylgermanium diiodide, di-ptolylgermanium difluoride, ethylgermanium triiodide, phenylgermanium tribromide, dicyclohexylgermanium dichloride, tolylgermanium trichloride, dimethyllead dichloride, diphenyllead dibromide and other known organometallic compounds which are generally described by R MX or RMX The insertion reaction wherein Group 4a metal dihalide is reacted with dicobalt octacarbonyl is believed to involve attack of the cobalt-cobalt bond by the metal dihalide such that the cobalt-cobalt bond is broken and two or more metalcobalt bonds are formed. The term insertion reaction" is generally descriptive of this operation without mechanistic implications. Insertion reactions are described more particularly by D. J. Patmore and W. A. G. Graham, inorganic Chemistry, Vol 5, No. 8, 1405 (1966) and in F. Bonati et al., J Chem. Soc. (A) 8, l052l055 (1968).

In the first step reactions employing sodium tetracarbonylcobaltate( l-), sodium amalgam is first interacted with dicobalt octacarbonyl to produce sodium tetracarbonyl cobaltate( l-), preferably in accordance with the method described by R. 8. King, organometallic Syntheses, l, 152 (1965). The reaction of the sodium tetracarbonylcobaltate( l-) with metal tetrahalide MX, or with organometallic halide, RMX or RMX is advantageously carried out according to the method described by D. J. Patmore et al., Inorg. Chem, Vol 6, 98] (1967).

In the practice of this invention the second step reaction of first step product with diolefin to produce the multinuclear, 'n'- complex is carried out by contacting the product of the first step with diolefin as described hereinbefore, preferably by dispersing the first step product into diolefin or its solution in an inert organic diluent such as n-pentane, dichloromethane, benzene and other hydrocarbon or halohydrocarbon solvents. it is also generally preferred to employ an excess of diolefin, e.g., from about 10 to about 1,000 moles of diolefin per mole of first step product, preferably from 25 to 500 moles. it is understood, however, that the second step reaction can be carried out by adding the reactants in any order with or without the presence of inert diluent or excess diolefin. During the second step reaction it is advantageous to stir or otherwise mix the reactants under an inert atmosphere such as nitrogen, helium and the like. Temperatures employed during this reaction suitably range from about 0 to 100 C, preferably from about 25 to about 75 C. The pressures employed can vary from about 1 to about 100 atmospheres, preferably from 1 to 2 atmospheres.

The period necessary to replace carbonyl with diolefin depends upon the amount of replacement desired. For example, ifa mono-diolefin rr-complex, e.g.,

is desired, the period required is from about 178 to about 6 hours, preferably 2 to 5 hours. However, if a bis-diolefin 1rcomplex, e.g.,

is desired, from about 6 to about 46 hours is required, preferably from 15 to 30 hours.

Both the first and second step reactions can be executed in a batch, semi-continuous, or continuous fashion. The reaction vessel can be a glass vessel, steel autoclave, elongated metallic tube, or other equipment and material employed in the art provided that such equipment is able to withstand the rigors of the reaction and that the reactants and products are not sensitive to this material of construction.

The novel multinuclear, 'rr-complexes of the present invention can be recovered easily by extracting the reaction product, usually an oily residue, with inert hydrocarbonsuch as n-pentane and subsequently recrystallizing the complex from the inert hydrocarbon extract. Other conventional methods for recovering crystalline organo-metallic compounds also may be employed. For the stable 1r-complexes liquid-solid chromatographic column packed with solid material, e.g., alumina, may also be used for purification.

The multinuclear rr-complexes wherein Z is halogen are particularly useful catalysts in the stereospecific dimerization of norbornadiene to form endo-cis-endo-heptacyclo[5.3.1.1 .1 .1 '.0 .0 ]tetradecane having the structure and hereinafter referred to as Binor-S. ln carrying out such stereospecific dimerization process, norbornadiene or substituted norbornadiene is contacted with the multinuclear 7rcomplex, preferably under an inert atmosphere such as nitrogen. Dimerization is suitably carried out at temperatures ranging from about 0 to 100C, preferably from 40 to 80C, and at pressures ranging from atmospheric to 100 atmospheres. The ratio of catalyst to norbornadiene or substituted norbornadiene employed ranges from about 0.001 mole of catalyst to about 0.05 per mole of norbornadiene, preferably from about 0.002 to 0.01, respectively. The dimerization period varies from about one minute to about 48 hours depending on the amount and species of catalyst, temperature and the like. Under the above specified conditions, more than 90 weight percent of norbornadiene dimer formed is Binor-S. Binor-S is particularly useful as a fuel additive and as a chemical intermediate for the preparation of other useful compounds.

The multinuclear, 'rr-complexes wherein Z is alkyl, aryl or another suitable organic ligand are found to dimerize norbornadiene to known dimers other than Binor-S. Such dimers are also useful as fuel additives and chemical intermediates. All of the multinuclear, rr-complexes of the invention are useful in the polymerization of other oletins and diolefins, for example, allene and c'yclopentadiene.

The following examples are given to illustrate the invention and should not be construed as limiting its scope. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 A 1.18 g-portion (2.2 mmoles) of dichlorobis-(tetracarbonylcobalt)tin(lV) (Cl Sn[Co(CO),,] prepared by reacting tin(ll) chloride with octacarbonyldicobalt is stirred with 10 g (110 mmoles) of norbornadiene at 60-65C under nitrogen atmosphere in a flask equipped with a condenser. After four hours under the above conditions an infrared spectrum of the reaction mixture indicates that Cl Sn[Co(CO),,] has been quantitatively converted to 'n-complex. By evacuation of the reaction mixture, more than 5 g of free olefin is recovered, leaving a blackish residue which is extracted with two l0-ml portions of n-pentane. The n-pentane extracts are combined and cooled in a dry ice bath for one hour. The mother liquor is then decanted and the blackish brown crystals in the flask are washed twice with cold n-pentane to yield 0.13 g of pure 1rcomplex.

The n-pentane extraction residue is further extracted with two 4-ml portions of methylene chloride. To the combined extracts ml of n-pentane is added and any floating solid formed is removed by centrifuging. Upon cooling of the solution in a dry ice bath for several hours, 0.62 g of the vr-complex is obtained. Further work-up on the mother liquor by evaporation and cooling gives additional 0.24 g of the product. The total yield of rr-complex is about 1 g (79 percent).

The 'rr-complex exhibits the following characteristics:

Analysis: %C %H Calculated for c|,snco,c,,H,o,= 27.5 1.41 Found: 28.18 1.36

Solubility: Very soluble in methylene chloride, fairly soluble in norbornadiene, cyclohexane, npentane. M.P.: Melts at with decomposition. 1R: Carbonyl stretching bonds at 2100(5),

2047(5), 2037(5), 2022(5), 201 1(5) and 1955(sh) cm". NMR: in trichlorodeuteromethanc solution, using tetramethylsilane as internal standard) 1' value (ppm) 5.81 (triplet), 6.40 (multiplet), 8.37 (triplet) Area Ratio: 2,1,1 respectively.

The above characteristics confirm the multi-nuclear rr-complex, dichloro(norbornadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(lV), Cl SnCo (C0)5(norbornadiene).

A 4.53-g portion (49 mmoles) of norbornadiene and 0.30 g (0.49 mmoles) of the above Ir-complex are changed to a flask equipped with a condenser at room temperature. After replacing air in the system with nitrogen, the contents of the flask are heated to 90C with stirring. Unreacted norbornadiene is removed by evacuating the flask leaving a black solid which is shown by gas chromatography to contain 90 percent Binor-S and 10 percent other known dimers of norbornadiene. The Binor-S is isolated by dissolving the black solid in dichloromethane, filtering the resultant solution through an alumina column, adding an equivalent amount of acetone, cooling and then filtering white crystals of Binor-S.

EXAMPLE 2 Under conditions similar to those used in Example 1, a 2.14- g. portion (3.45 mmoles) of dibromobis(tetracarbonylcobalt)tin(lV) is reacted with 20 g (220 mmoles) of norbornadiene. Following the recovery procedure of Example 1, blackish brown crystals of a ar-complex are obtained at a yield of 1.51 g (63 percent yield). The resulting ar-complex exhibits the following characteristics:

Analysis: %C %H Calculated for Br SnC0,C H,,0 23.78 1.22 Found: 24.21 1.11

Solubility: Similar to that of Cl,SnCo,(

CO)B (norbornadiene) 1R: Carbonyl stretching bands at 2099(s),

2045(s), 2036(s), 2021(5), 2010(5), and 1995(sh) cm". NMR: 1' value (ppm) 5.58 (triplet), 6.42

(multiplet), 8.37 (triplet) Area Ratio: 2,1,1 respectively.

The above characteristics confirm the multinuclear rr-com plex, dibromo(norbornadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(lV), a Br SnCo (CO) (norborna-diene).

The above catalyst dimerizes norbornadiene to Binor-S when the dimerization procedure described in Example 1 is employed.

EXAMPLE 3 A 2.16-g portion (4.1 mmoles) of Cl,Sn[Co(CO) and 10 g mmoles) of norbornadiene are stirred at 60 C under nitrogen in a reaction flask equipped with a condenser. After 24 hours an additional 10 g of norbornadiene is added and the reaction is continued for another 24 hrs. A trace of free olefin is removed by evacuation, leaving a blackish solid which is washed with six 15-ml portions of cyclohexane on a suction funnel. The blackish sludge-like residue is then extracted with 15-ml portions of norbornadiene until the infrared spectrum of the extract shows no carbonyl stretching bands. The extracts are combined and the volume is reduced to about 30 ml. On cooling of the solution at 0C overnight, blackish red crystals of rr-complex are formed. The mother liquor is decanted and the crystals (0.5 g) are washed several times with cyclohexane. Further concentration and cooling of the mother liquor yields an additional 0.1 l g of the product, resulting in a total yield of rr-complex of 0.61 g (25 percent yield). The 1rcomplex exhibits the following characteristics:

Analysis: %C 11H Calculated for Cl,SnCo,C l-l,,O,: 35.8 2.66 Found: 35.95- 2.47- 36.26 2.61

Solubility: Very soluble in acetone (with decomposition) and methylene chloride, less soluble in norbornadiene, and much less soluble in non-polar solvcnts. M,l.: Turns to purple-gray at IMP-140C without melting.

lR: Carbonyl stretching hands at 2034(s),

2005(m), l984(s)and l97(l(sh) emf.

NMR: 1 value (ppm) 5.82 (triplet), 6.45

(multiplet), 8.64 (triplet) Area Ratio: 2,1,1 respectively.

X-ray: The molecular structure of the compound is determined by the Patterson and Fourier methods. Refinement is made by fullmatrix least-squares assuming an isotropic temperature for the Sn, C1, C0, C and O atoms gave an R-factor of4.9 percent for 2977 reflections measured above background level on a Picker automatic diffractometer (MOKa radiation). Accordingly, the molecular structure is as follows:

Accordingly, the multinuclear rr-complex, dichlorobis(norbomadienedicarbonylcobalt)tin(IV); Cl,SnCo,(CO) (C-,l-l is confirmed.

The above rr-complex show similar catalytic activity to those described in Examples 1 and 2.

EXAMPLE 4 Reaction of Br,Sn[Co(CO),] and norbornadiene under conditions similar to those described in Example 3 yields a 1rcomplex which shows infrared and nmr spectra very similar to those of Cl,Sn[Co(CO) (NBD)],. The multinuclear yr-complex, dibromobis(norbornadienedicarbonylcobalt)tin(lV) is thus confirmed. This rr-complex exhibits a catalytic activity similar to those described in Examples 1-3.

EXAMPLE 5 A 2.07-g portion (3.26 mmoles) of diphenylbis-(tetracarbonylcobalt)tin(lV), (phenyl) Sn[Co(CO),],, prepared by reacting diphenyldichlorotin(IV) with sodium tetracarbonylcobaltate(1-) in tetrahydrofuran is stirred with g (110 mmoles) of norbornadiene at 60C under nitrogen in a flask equipped with a condenser. After 24 hours, an additional 10 g of norbornadiene is added and the reaction is continued for another 24 hrs. The blackish tar-like reaction mixture is extracted with five -ml portions of n-pentane. The extracts are combined and filtered through an alumina column (1% in. in diameter, 1 in. in length). The volume of filtrate is reduced to 10 ml by evaporation with a flow of nitrogen and any solid formed is removed by centrifuging. The supernatant liquid is then chromatographed on an alumina column (three-fourths in. in diameter, 10 in. in length) using n-pentane as eluent. Only one yellowish orange band is observed moving down the column. This fraction is collected and gradually evaporated to dryness with a flow of nitrogen. After the residue has been extracted several times with cold n-pentane, reddish brown solid is obtained at the bottom of the flask. Infrared analysis indicates that the solid is pure rr-complex. The yield is 0.22 g. (10 percent yield).

Recrystallization of the rr-eomplex is effected by dissolving the crude product in a minimum volume of norbornadiene followed by addition of an equal volume of n-pentane. Reddish brown, prismatic crystals are obtained on cooling of the solution at 0 for several hours. The 1r-complex exhibited the following characteristics:

Crushed powder:

IR: Carbonyl stretching bands at 2008(m 1989(s),1957(s), 1947(sh) emf. NMR: (7 value ppm) 2.35, 2.82 (due to the phenyl 6.15, 6.67, 8.86 (due to (NBD).

groups) The above characteristics confirm the multinuclear, rr-complex, diphenylbis(norbornadienedicarbonylcobalt)tin(lV).

When the above 'rr-complex is employed in the dimerization procedure described in Example 1, known dimers of norbornadiene other than Binor-S are formed.

EXAMPLE 6 A 1.09-g portion (1.75 mmoles) of Br Sn[Co(CO) and 18.5 g (340 mmoles) of 1,3-butadiene in 6 ml of dichloromethane are sealed under vacuum in a Carius tube equipped with a poly(tetrafluoroethylene) stopcock. The tube is heated to about 60 to 65C for one day followed by cooling to -196C and evacuation to remove CO gas formed. The same heating and evacuation process is repeated each day for three consecutive days. After the end of the reaction, the volatile liquid is removed by evacuation. The resulting black residue is dissolved in a minimum volume of dichloromethane and the solution is centrifuged and the supernatant solution is decanted. To the supernatant solution about three parts of npentane is added with stirring and the resulting solution is gradually cooled to dry ice temperature. After three hours the mother liquor is decanted and the resulting reddish black crystals are washed twice with cold n-pentane and dryed with a flow of nitrogen. The yield is 0.32 g. The decanted mother liquor is slowly evaporated to dryness with a flow of nitrogen. The residue is extracted twice with n-pentane. The extraction residue is dissolved in a minimum volume of dichloromethane, following by addition of n-pentane and cooling in a dry ice bath to produce more reddish black crystals. A total yield of 0.44 g (40 percent) is observed.

The reddish black crystals are purified by recrystallization from a dichloromethane/n-pentane system and are identified by elemental analysis and infrared and NMR data to be the 1rcomplex, dibromo 1 ,3-butadienedi-carbonylcobalt)(tetracarbonylcobalt)tin(IV Br,Sn[Co(CO) )z( 4 s)]- The above rr-complex is an active catalyst in the dimerization of norbornadiene to Binor-S and in the polymerization of allene.

EXAMPLE 7 A 0.23-g portion (0.43 mmoles) of Cl Sn[Co(CO) and 8.1 g (150 mmoles) of 1,3-butadiene in 5 ml of dichloromethane are heated under vacuum at 75C in a sealed Carius tube for hours. The tube is vented and volatile components removed under reduced pressure. The residue is extracted with dichloromethane several times and the combined extracts are allowed to evaporate slowly until almost dry. Washing of the solid with cyclohexane affords 0.03 g (13.2 percent) of reddish brown needles which are shown by elemental and spectral analyses to be the rr-complex, dichlorobis(1,3-butadienedicarbonylcobalt)tin(lV), 2 )z( 4 s)l2- The above 'rr-complex is an active catalyst in the dimerization of norbomadiene to Binor-S and in the polymerization of allene.

EXAMPLE 8 A 1.03-g portion (1.9 mmoles) of Cl Sn[Co(CO),'] and 14 g (152 mmoles) of norbomadiene in 15 ml of methylene chloride are stirred overnight at 50C under nitrogen atmosphere. Following the work-up procedure of Example 1, 0.8 g (72 percent yield) of dichloro(norbornadienedicarbonylcobalt)(tetracarbonylcoba1t)tin(1V) is isolated.

EXAMPLE 9 A 0.066-g portion (0.16 mmoles) of diphenylbis-(tetracarbonylcobalt)germanium(IV) prepared by reacting diphenylgermanium(IV) dichloride with large excess of sodium tetracarbonylcobaltate( l) is stirred with 1.3 g (14.1 mmoles) of norbomadiene at 75-80C for 12 hours under nitrogen atmosphere. Spectroscopic examination including a careful examination of the carbonyl stretching frequencies of the reac tion mixture reveals that the starting germanium complex is converted entirely to diphenylbis(norbomadienedicarbonyl cobalt)germanium(lV). This multinuclear, 'rr-complex dimerizes norbomadiene to form several known dimers of norbomadiene.

EXAMPLE 10 v A 0.59 g portion (0.93 mmoles) of dibromobis-(tetracarbonylcobalt)tin(lV) and 3.96 g (49.5 mmoles) of cyclohexa- 1,3-diene are stirred at 70C for about 2% hours under nitrogen. The volatile organic components of the resulting reaction mixture are removed under reduced pressure, and the remaining residue is washed with 5 ml of n-pentane and is then extracted with two 2-ml portions of dichloromethane. To the combined extracts is added 8 ml of n-pentane with stirring. Any floating material in resulting supernatant liquid is removed by centrifugation and the liquid is cooled to 78C. After 3 hours, 0.33 g (52 percent yield) of flaky, brown crystalline product is recovered.

The brown crystalline product is found to be a ar-complex having the following characteristics:

Analysis: %C %H Calculated for Br,snco,c,,H,0,: 22.36 1.25 Found: 23.25 1.85

Solubility: Slightly soluble in non'polar solvents and very soluble in polar solvents. M.P.: Decomposed without melting at 108l 12C to give a greenish gray solid. 1R: Carbonyl stretching frequencies (cm") at 2096(5), 2057(5), 2042(s), 2025(s), 2013(m) and 1996(m).

The above characteristics confirm the multi-nuclear 1r-c0mplex dibromo(cyclohexa-l ,S-dienedicarbonylcobalt)(tetracarbonylcobalt)tin(1V), Br SnCo (CO) 1,3- C H This rr-complex dimerizes norbomadiene to Binor-S when employed in the dimerization of Example 1.

EXAMPLE 11 A 1.23-g portion (1.97 mmoles) of dibromobis-(tetracarbonylcobalt)tin(lV) and 4 g (50 mmoles) of cyclohexa-l,3- diene are stirred at 90C for about 2 hours under nitrogen. After the volatile organic components are removed under reduced pressure, an additional 4 g (50 mmoles) of cyc1ohexa-1,3-diene is added to the residue and the resulting solution is heated 2 hours at 8590C. The above volatization of organic components, addition of cyclohexa-l,3-diene and heating of the solution is repeated. After removing volatile components, the resulting black residue is washed with 15 m1 of n-pentane and then extracted with two 2-ml portions of methylene chloride. Recrystallization from the combined extracts yielded 0.11 g (8.1 percent yield) of pure rr-complex having the following characteristics:

Analysis: %C %H Calculated for Br SnCo C H O 28.74 2.41 Found: 28.91 2.53

Solubility: Slightly soluble in n-pentane, very soluble in methylene chloride and other polar solvents. M.P.: 132-133 with decomposition. 1R: Carbonyl stretching frequencies (cm") 2051(5), 2025(m to s), 2005(m,b), and 1995(Sb).

The above characteristics confirm the multinuclear,1r-complex, dibromobis(cyclohexal ,3-dienedicarbonyl- A l-g portion (1.5 mmole) of ch1orotris(tetracarbonylcobalt)tin(lV) prepared by reacting SnCl with Co (CO) in molar ratio of 1:2 is stirred with 9 g (98 mmoles) of norbornadiene at 65-70C for 7 hours under nitrogen. The resulting ir-complex is isolated from the reaction mixture using the procedure set forth in Example 1. Spectroscopic examination and the elemental analysis of the 'rr-complex confirms the multinuclear, 'rr-complex of chloro(norbornadienedicarbonylcobalt)bis(tetracarbonylcobalt)tin(1V), ClSnCo (CO) ,(C H This ar-complex is an effective catalyst for the dimerization of norbomadiene.

EXAMPLE 13 A 1.2-g portion (1.5 mmole) of tetrakis(tetracarbonylcobalt)tin(lV) prepared by reacting SnF with Co (CO) in molar ratio of 1:1 is stirred with 9 g (98 mmoles) of norbornadiene at 6570C for 7 hours under nitrogen. The resulting rr-complex is isolated from the reaction mixture using the procedure described in Example 1. Spectroscopic examination and elemental analysis of the rr-complex confirms the multinuclear, rr-complex of (norbornadienedicarbonylcobalt)tris(tetracarbonylcobalt)-tin(1V) SnCo -,(CO), (C H,,). This rr-complex is an effective catalyst for the dimerization of norbomadiene.

Similar multinuclear, 'rr-complexes containing other Group 4a metals, other ligands and other 'rr-ligands are prepared by techniques similar to those described above. All are active catalysts in the dimerization of norbomadiene.

What is claimed is:

1. A multinuclear rr-complex having at least two metalcobalt bonds represented by the general formula:

4-m m( )4m-2n wherein M is a metal of Group 4a of the Periodic Table of Elements; Z is a ligand selected from the group consisting of halo, nitrato, alkyl and substituted alkyl wherein the substituent is aryl, halo, alkyoxy or amino, cycloalkyl, aryl and substituted aryl wherein the substituent is alkyl, halo, alkoxy or amino; Y

is a rr-bonded diolefin ligand having from four to eight carbon atoms selected from the group consisting of acyclic conjugated alkadienes, alkoxysubstituted acyclic conjugated alkadienes, cyclic alkadienes, aryl substituted acyclic conjugated alkadienes, polycyclic alkadienes; m is 2, 3, 4 and n is l, 2, 3, or 4, but not greater than m.

2. A multinuclear 'IT-COmPlEX according to claim 1 having at least two metal-cobalt bonds represented by the general formula:

wherein M is a metal of Group 4a of the Periodic Table of Elements; Z is a ligand selected from the group consisting of halo, nitrato, methyl, ethyl, propyl, butyl, cyclohexyl, phenyl, benzyl, and tolyl, Y is a rr-bonded diolefin ligand selected from the group consisting of buta-l,3,-diene, isoprene, pental,3-diene, 2,3-dimethylbuta-l,3-diene, hexa l ,3- and hexal ,4- diene,0cta-2,4-diene, 2-methylpenta-l,3-diene, 2 methoxybuta-l,3-diene, 2,3-dimethoxybuta-l,3-diene, 2-methoxy-3- ethoxypenta-l,3-diene, cyclopentadiene, cyclohexa-l,3- diene, cycloocta-l,3-diene, cyclohexa-l,4-diene, cyclohepta- 1,3-diene, cyclohepta-l ,4-diene, cycloocta-l,5diene, 1,4- diphenylbuta-l,3-diene, norbornadiene, bicyclo[2.20]hexa- 2,5-diene, spiro[4.4]nona-l,3-diene, spiro[4.2]hepta-l,3- diene, bicyclo[4.2.0]octa-2,4-diene, bicyclo[3.3.0]octa-l,3- diene, and bicyclo[3.2.l ]octa-2,6-diene, m is 2, 3, or 4 and n is l, 2, 3, or 4, but not greater than m.

3. The rr-complex according to claim 1 wherein Z is chloro.

4. The Ir-complex according to claim 1 wherein Z is bromo.

5. The ir-complex according to claim 1 wherein Z is phenyl.

6. The rr-complex according to claim 1 wherein M is tin.

7. The ir-complex according to claim 1 wherein M is germanium.

8. The rr-complex according to claim 1 wherein Y is norbornadiene.

9. The rr-complex according to claim 1 wherein Y is l,3-butadiene.

10. The complex according to claim 1 wherein Y is cyclohexa-l ,3-diene.

11. The complex according to claim 1 wherein the complex is dichlorobis(norbornadienedicarbonylcobalt)-tin(IV).

12. The complex according to claim 1 wherein the complex is dibromobis(norbornadienedicarbonylc0balt)-tin( IV).

13. The complex according to claim 1 wherein the complex is diphenylbis(norbornadienedicarbonylcobalt)-tin(lV).

14. The complex according to claim I wherein the complex is dibromo(norbornadienedicarbonylcobalt)-(tetracarhonylcobalt)tin(lV).

15. The complex according to claim I wherein the complex is dichloro(norbornadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(lV).

16. The complex according to claim I wherein the complex is dibromo( l ,3-butadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(lV).

17. The complex according to claim] wherein the complex is dichlorobis( l ,3-butadienedicarbonylcobalt)-tin( lV 18. The complex according to claim I wherein the complex is dibromo(cyclohexa-l,Z-dienedicarbonylcobalt)-(tetracarbonylcobalt)tin(lV). 1

19. The complex according to claim 1 wherein the complex is diphenylbis(norbornadienedicarbonylcobalt)-germanium(lV).

20. The complex according to claim 1 wherein the complex is dibromobis(cyclohexa-l ,3-dienedicarbonylcobalt)tin(IV).

21. The complex according to claim I wherein the complex is chloro(norbornadienedicarbonylcobalt)bis-(tetracarbonylcobalt)tin(lV).

22. The complex according to claim 1 wherein the complex is (norbornadienedicarbonylcobalt)tris(tetracarbonylcobalt)tin(lV). 

2. A multinuclear pi -complex according to claim 1 having at least two metal-cobalt bonds represented by the general formula: Z4 mMCom(CO)4m 2nYn wherein M is a metal of Group 4a of the Periodic Table of Elements; Z is a ligand selected from the group consisting of halo, nitrato, methyl, ethyl, propyl, butyl, cyclohexyl, phenyl, benzyl, and tolyl, Y is a pi -bonded diolefin ligand selected from the group consisting of buta-1,3,-diene, isoprene, penta-1, 3-diene, 2,3-dimethylbuta-1,3-diene, hexa1,3- and hexa-1,4-diene, octa-2,4-diene, 2-methylpenta-1,3-diene, 2 methoxybuta-1,3-diene, 2,3-dimethoxybuta-1,3-diene, 2-methoxy-3-ethoxypenta-1,3-diene, cyclopentadiene, cyclohexa-1,3-diene, cycloocta-1,3-diene, cyclohexa-1,4-diene, cyclohepta-1,3-diene, cyclohepta-1,4-diene, cycloocta-1,5-diene, 1,4-diphenylbuta-1,3-diene, norbornadiene, bicyclo(2.20)hexa-2,5-diene, spiro(4.4)nona-1,3-diene, spiro(4.2)hepta-1,3-diene, bicyclo(4.2.0)octa-2,4-diene, bicyclo(3.3.0)octa-1,3-diene, and bicyclo(3.2.1)octa-2,6-diene, m is 2, 3, or 4 and n is 1, 2, 3, or 4, but not greater than m.
 3. The pi -complex according to claim 1 wherein Z is chloro.
 4. The pi -complex according to claim 1 wherein Z is bromo.
 5. The pi -complex according to claim 1 wherein Z is phenyl.
 6. The pi -complex according to claim 1 wherein M is tin.
 7. The pi -complex according to claim 1 wherein M is germanium.
 8. The pi -complex according to claim 1 wherein Y is norbornadiene.
 9. The pi -complex according to claim 1 wherein Y is 1,3-butadiene.
 10. The complex according to claim 1 wherein Y is cyclohexa-1,3-diene.
 11. The complex according to claim 1 wherein the complex is dichlorobis(norbornadienedicarbonylcobalt)-tin(IV).
 12. The complex according to claim 1 wherein the complex is dibromobis(norbornadienedicarbonylcobalt)-tin(IV).
 13. The complex according to claim 1 wherein the complex is diphenylbis(norbornadienedicarbonylcobalt)-tin(IV).
 14. The complex according to claim 1 wherein the complex is dibromo(norbornadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(IV).
 15. The complex according to claim 1 wherein the complex is dichloro(norbornadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(IV).
 16. The complex according to claim 1 wherein the complex is dibromo(1,3-butadienedicarbonylcobalt)-(tetracarbonylcobalt)tin(IV).
 17. The complex according to claim 1 wherein the complex is dichlorobis(1,3-butadienedicarbonylcobalt)-tin(IV).
 18. The complex according to claim 1 wherein the complex is dibromo(cyclohexa-1,3-dienedicarbonylcobalt)-(tetracarbonylcobalt)tin(IV).
 19. The complex according to claim 1 wherein the complex is diphenylbis(norbornadienedicarbonylcobalt)-germanium(IV).
 20. The complex according to claim 1 wherein the complex is dibromobis(cyclohexa-1,3-dienedicarbonylcobalt)tin(IV).
 21. The complex according to claim 1 wherein the complex is chloro(norbornadienedicarbonylcobalt)bis-(tetracarbonylcobalt)tin(IV).
 22. The complex according to claim 1 wherein the complex is (norbornadienedicarbonylcobalt)tris(tetracarbonylcobalt)tin(IV). 